1. Field of the Invention
The field of invention relates to a drill string device and method of use. More specifically, the field relates to disconnecting and reconnecting a drill string and method of use.
2. Description of the Related Art
In horizontal drilling, there are many challenges to maintaining operations in non-vertical or deviated systems. Gravity pulls the drill pipes, collars, bit and tools against the well bore wall, causing friction while drilling. In extended-reach wells (ERWs), well bore collapses, stress fracturing and breaking of long drill strings, poor fluid circulation along the length of the well bore and solids accumulation can trap a drill string. Halting the rotation of the drill string further exacerbates the friction problem.
When a drill string becomes stuck downhole, a few methods are employed before declaring the string lost. An in-line mechanical jar, hydraulic drilling jar or hydro-mechanical jar can provide an acute physical “shock” along the drill string axis. The force of the discharging jar suddenly shifts or pulls the drill string along the length of the well bore, dislodging it. Increasing drilling fluid circulation can provide fluid lift to the drill string and can erode solids that have blocked off drill string movement. “Pulsing” the drill string with rapid, successive rotational turns can shift obstructions and free the string.
Potentially a number of problems exist with simply increasing drilling fluid flow in a horizontal well, especially an ERW to treat a well bore condition. The fluid exiting the end of the drill string has traveled hundreds or thousands of meters—in some cases several kilometers—before passing into the well bore. To address the problem, the fluid then has to travel possibly thousands of more meters in the well bore annulus before encountering the well bore condition. Some ERWs have horizontal runs beyond 35,000 feet. This requires a tremendous amount of energy to reach this problem site, usually in the form of higher fluid pressure. Well bore conditions, including pore pressure and fracture gradient, can severely limit the maximum pressure of the drilling fluid passing from the drill pipe against the face of the distal end of the well bore.
If these simple operational techniques do not work, a wireline, coiled tubing or slick line crew can intervene and sever the drill string while in the hole. These teams often use specialized tools specifically manufactured for the job. Sometimes explosive are employed. The cost of such a recovery operations depends on many factors, including the physical location of the well bore (country; on or off-shore), local regulations, formation and well bore structure, transportation of personnel and equipment, government and corporate permission to execute the job; manufacturing time for specialty tools, and ancillary support operations, including fishing or well bore circumvention. Such intervention can run from a few hours to weeks of drilling and completions time, with idle work crews, delays in scheduled production of hydrocarbon fluid and the loss of expensive downhole tools, including the drill bit, hundreds if not thousands of feet of drill pipe, collars and the borehole assemblies (BHA). The total cost can reach into the millions of dollars per instance.
Disconnection tools have a long history in the petroleum drilling service industry. Several types have come to prominence over the years, including those having shear-release, pressure-release and electrically controlled mechanisms. Shear and pressure disconnectors activate by either a build-up in pressure caused by introducing a restriction inside the throat of the tool, for example, a ball, dart or plug, or by using a predefined overpull or drill string turn sequence that initiates a mechanical release. Electrical disconnectors use wires from the surface through the drill string or by wireline or coiled tube. All of these disconnectors are “one-use”: once they disconnect two sections of drill string they cannot be recombined.
Disconnect tools have several inherent problems related to horizontal, ERW, multilateral and multi-tier well bore drilling. Conventional methods of freeing at least a portion of a stuck drill string are less appropriate in long-reaching horizontal well bores and in multi-lateral wells. In horizontal wells, the main problems are friction and gravity over the long horizontal leg. The designs of many tools are for operation in vertical environments and only over short distances—a few thousand feet. Many tools and techniques requiring wireline or coiled tubing access to disconnect or sever the drill string. These tools are problematic due to both the direction of gravity versus the direction of the well bore (that is, pulling the tube to the bottom of the well bore) and friction against the well bore wall (requiring much more force to drive the intervening tool). In multilateral and multi-tier well bores, these tools and methods are very difficult if not impossible to use.